Suppose I'm talking to someone directly, and use a pronoun to refer to someone. I would use tu or vōs with an appropriate case based on its role in the sentence: for example, sciō tē adesse, "I know that you are here", with the accusative.
But what if I'm using a noun (such as a name or a description) along with that pronoun? My instinct is to put it in the same case. But a line from the Roman Missal is making me doubt that:
Confiteor Deo omnipotenti […] et vobis, fratres…
I confess to almighty God […] and to you, my brothers…
Here, fratrēs is in the vocative, even though vōbīs right next to it is dative.
Is this correct, by the standards of Classical Latin prose? And would it be incorrect to use fratribus instead?
(The quote is from the beginning of the Confiteor.)